Engines, including diesel engines, gasoline engines, gaseous fuel powered engines, and other engines known in the art exhaust a complex mixture of air pollutants. These air pollutants include solid material known as particulate matter or soot. Due to increased attention on the environment, exhaust emission standards have become more stringent and the amount of particulate matter emitted from an engine is regulated depending on the type of engine, size of engine, and/or class of engine.
One method implemented by engine manufacturers to comply with the regulation of particulate matter exhausted to the environment has been to remove the particulate matter from the exhaust flow of an engine with a device called a particulate trap or diesel particulate filter. A particulate trap is a filter designed to trap particulate matter and typically consists of a wire mesh or ceramic honeycomb medium. However, the use of the particulate trap for extended periods of time may cause the particulate matter to build up in the medium, thereby reducing the functionality of the filter and subsequent engine performance.
The collected particulate matter may be removed from the filter through a process called regeneration. To initiate regeneration of the filter, the temperature of the particulate matter trapped within the filter must be elevated to a combustion threshold, at which the particulate matter is burned away. One way to elevate the temperature of the particulate matter is to inject a catalyst such as diesel fuel into the exhaust flow of the engine and ignite the injected fuel.
After the regeneration event, the supply of fuel is shut off. However, some fuel may remain within the fuel injector or the fuel lines that direct fuel to the injector. This remaining fuel, when subjected to the harsh conditions of the exhaust stream may coke or be partially burned, leaving behind a solid residue that can restrict or even block the fuel injector. In addition, it may be possible for particulate matter from the exhaust flow to enter and block the injector. For this reason, it may be necessary to periodically purge the injector of fuel and/or any built up residue or particulate matter between regeneration events.
One method of purging a fuel injector is described in U.S. Pat. No. 4,987,738 (the '738 patent) issued to Lopez-Crevillen et al. on Jan. 29, 1991. Specifically, the '738 patent discloses a particulate filter having a burner used to incinerate trapped particulates. The burner includes a fuel injector nozzle for injecting fuel into the burner during regeneration. As illustrated in FIG. 1 of the '738 patent, a fuel pump supplies fuel to the injector nozzle via a passageway axially aligned with a bore of the nozzle. In order to maintain efficient and reliable operation of the burner, a supply of purge air is directed through the axially aligned passageway to the fuel injector nozzle following a regeneration event to purge the nozzle of fuel. Purge air continues to flow through the injector nozzle until a subsequent regeneration event.
Although the burner of the '738 patent may benefit somewhat from the purging process described above, the gain may be more expensive. In particular, the additional passageways required to support the air purging may increase machining cost, component cost, and assembly time. And, the continuous flow of purge air may be expensive to maintain and increase the risk of debris fowling the injector nozzle.
The method of the present disclosure solves one or more of the problems set forth above.